package demo3;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] cost = new int[n];
        for(int i = 0; i<n; i++) {
            cost[i] = scanner.nextInt();
        }
        int[] dp = new int[n+1];
        for(int i = 2; i<=n; i++) {
            dp[i] = Math.min(dp[i-1]+cost[i-1],dp[i-2]+cost[i-2]);
        }
        System.out.println(dp[n]);
    }
}
